Brake control means



Aprll4, 1942. B. s. AIKMAN BRAKE CONTROL MEANS Filed Aug. 51, 1939 3 SheetS-Sheet 1 INVENTOR BURTON 5. A|KMAN www, 9M

' ATTORNEY B. s. AIKMAN *l BRAKE CONTROL MEANS April 14, 1942.

Filed Aug. 5l, 1959. 5 Sheets-Sheet 2 .CNN N www n: NNN

INVENTOR BURTON 5. AIKMAN ATTORNEY April 14, 1942. B. s. AIKMAN 2,279,432

BRAKE CONTROL MEANS Filed Aug. 3l', 1959 3 Sheets-Sheet 3 2|7\ 225 24o Q16 Q45 m5 'lNvENToR BURTDN S. AIKMAN ATTORN EY o Mom 55"@ '5m @abili Patented Apr. 14, 1942 UNITED STATES NT ortica BRAKE CONTROL MEANS Application August 31, 1939, Serial No. 292,831

` 7 claims. (ci. 303-21) This invention relates to vehicle brake systems, and more particularly to a fluid pressure brake equipment embodying means responsive to the braking torque effective on a wheel for controlling the force with which the brakes are applied.

It has been proposed to provide brake apparatus for a vehicle, including mechanism automatically operative in accordance with the torque produced by cooperation of a rotating member with a relatively stationary brake member for preventing the braking force from exceeding a predetermined value, thereby avoiding sliding-of the vehicle wheels. Adequate control of the brakes for certain classes of railway service may be obtained with braking apparatus operative on this principle, in which movement of a torque responsive member is utilized to limit the degree of the brake application so as to prevent the locking of the wheels. However, the requirements of lother classes of service are such that they are met only by providing a brake equipment embodying torque control means of the above type which is operative to control the application of the .brakes on individual Wheel and axle units over a range of different degrees of braking force, the desired degree of brake application being at all times under the control of the engineer.

It is a principal object of the present invention to provide a torque controlled brake equipment having the desirable features above mentioned.

Another object of the invention is to provide` a fluid pressure brake equipment including means responsive to the torque exerted on Wheel brake devices for regulating the degree of brake application on an individual wheel and axle unit to any one of a plurality of different values selected by the engineer. l

A further object of my invention is to provide an electro-pneumatic brake apparatus by operation of which the application of the brakes may be effected to various degrees according to the pressure of iiuid in a control pipe as determined by the engineer, while the braking force with which the brakes are applied on individual Wheels is automatically limited to a safe value in accordance with the braking torque produced.

It is also an object of this invention to provide a torque controlled fluid pressure brake apparatus of the above type which-may readily be designed and adapted for useV on a vehicle having clasp brake rigging, or on a vehicle equipped with a so-called .disk brake apparatus of Fig. 4.

having interleaved stationary and rotatable braking elements.

Other objects and advantages of the invention will appear in the following more detailed description thereof, taken in connection with the accompanying drawings, wherein Fig. 1 is a diagrammatic elevational view of one form of brake equipment for a vehicle wheel constructedin accordance with the invention;

Fig. 2 is a reduced detail fragmentary plan view of the wheel and associated braking elements shown in Fig. 1;

Fig. 3 is a sectional View taken' on the line 3-3 of Fig. 1;

Fig. 4 is a diagrammatic elevational View of another form of vehicle brake equipment constructed in accordance with the invention;

Fig. 5 .is va View of the brake control switch device shown in Fig. 4, illustrating the device ina different operative position;

Fig. 6 is an end view, partly in section, of the wheel and associated brake elements shown in Fig. 4; and

Fig. '1 is an enlarged detail sectional view of the control switch Equipment shown in Figs. 1 and 2 Referring to Fig. 1 of the drawings, one form of brake control apparatus embodying my invention is therein illustrated in association with a vehicle truck having clasp brake rigging. Included in the drawings is a Vehicle wheel li) secured to .an axle mounted in a suitable journal structure ll, on Which is supported in the usual manner a vehicle truck, which-is illustrated in fragmentary form and comprises a side frame member 4l2 having the usual pedestal jaw portions 4I3 Awithin whichy the journal structure H is mounted. The clasp brake rigging includes a pair ofbrake shoes and heads I6 and Il, which are disposed atopposite sides of the wheel lll pin 24, hanger member 25, pin 26 and lever 2'l,

which is alignedwith the lever 2| and is pivotally connected by means of a pin 28 to the-side frame member.

device taken on the line 1-1 The brake head |1 is operatively connected by means of a pin 30 to a brake lever 3|, the upper end of which is pivotally connected -by a pin 32 to the piston rod 33 of a brake cylinder device 34, the piston rod being relatively loosely mounted within a sleeve member 35 which is adapted to be actuated by the brake cylinder piston, not shown. The 'lower end of the brake lever 3| carries a pin 38 to which are connected the adjacent ends of a pair of tie rods 39, which are horizontally disposed at opposite faces of the Wheel I and have their other ends pivotally connected by means of a pin 4| to a lever 42. The lever 42 has a slot 43 formed in the upper end thereof for receiving` a pin 44 which is carried by the truck frame structure, and is pivotally connected intermediate its ends by means of a pin 45 to the brake head I6. It will be understood that the brake heads and shoes I6* and |1 are thus supported through the medium of the respective hanger members |97 and 25, and that the levers 22 and 3| together with the tie rods 39 do not support the shoes but are adapted to be operated to effect application of the shoes against the wheel I0, as hereinafter explained.

According to the invention, the reactive force to which the brake shoes I6 and I1 are subjected during an application of the brakes is transmitted, as hereinafter explained, through the medium of the respective levers 2| and 21 to the mechanism of a control switch device 50, which is adapted to be conditioned in accordance with the pressure of uid'supplied to a control pipe I, which may extend throughout the train, by operation of a self-lapping brake valve device 52. The switch device 50 controls circuits for a magnet valve device 54, which in turn is adapted to control the supply and release of fluidr under pressure to and from the brake cylinder device 34. The self-lapping brake valve device may be similar to that disclosed in United States Patent 2,042,112 to Lynn and Bush, issued May`26, 1936.

The control switch device 5 0 comprises a casing 56, which may be disposed above the journal structure of the truck and securedto the side frame member |2 'in any suitable manner, as by bolts 51 shown in Fig.l 2 of -the drawings, the lowermost portion of thecasing extending downwardly into the plane of the levers 2|' and 21, which are suitably curved to clear the adjacent rim of the wheel I0 as shown. The inner `ends of the levers 2| and 21 vextend through suitable apertures in the casing 56 into a chamber 6| therein, the lever 21 having a clevis portion 62 formed on the end thereof for vreceivingv the adjacent end 63 of the lever 2|. Itwill thus be apparent that either lever may be tilted about the pivotal connection thereof with the side frame member so as to raise the inner end of that lever within the chamber 6| without effecting the other lever. The clevis portion 62 and the end 63 of the respective levers both are normally adapted to rest on a stop lug 65 formed on the casing 56 within the chamber 6|.

Clamped between the casing 56 and a cover plate 61 is a flexible diaphragm 68, which has formed at the upper side thereof a chamber 69'` communicating with the control pipe 5|, and is engaged at its lower side by a follower member having a stem 1| projecting downwardly throughl a suitable bore formed in a wall 12 of the casing and into the chamber 6|. Upward movement of diaphragm 68 is limited by a plurality of stop lugs 13 carried by cover plate 61. The end of the stem 1| within the chamber 6| is operatively aligned with both the clevis portion 62 of the lever 21 and the end 63 of the lever 2|, suitable shock absorbing means, such as a spring 14, being interposed between the end of the stem and the levers, through the medium of which shock absorbing spring movement of either lever can be transmitted to the stem as hereinaftermore fully explained.

f The control switch device r5|) further comprises a substantially horizontally disposed lever 16 which is pivotally mounted on a pin 11 carried by the casing 56 within an aperture 18 therein, which lever has the inner end 19 thereof inserted in a slot 8 0 formed in the stem 1|.' The outer end of the lever 16 has formed thereon a clevis portion 82, through which extends the lower end of a vertically disposed rod 83 having collar portions 84 and 85 formed thereon to engage the clevis portion. The rod 83 is slidably mounted in a suitable bore formed in a bracket portion 81 of the casing 56, and carries at the upper end thereof a suitably insulated switch contact member 88, which is adapted to engage a switch contact element 89 mounted on the cover plate 61, while the vvarious elements of the control switch device 50 are in their normal positions as illustrated. lThe cover plate 61 has a bracket portion 9| on which is mounted a suitably insulated switch contact element 92, which is operatively aligned with contact member 88, and is spaced from the switch contact element 89 by a sunlcient distance to permit positioning of the contact member 88 in an intermediate position in which it engages neither of the two contact members.

The magnet valve device 54 comprises a pipe bracket `95 having secured to oneface thereof a release magnet valve portion 96 and to the other face thereof an application magnet valve portion 91. The magnet valve portion 96 has formed therein avalve chamber |00 communicating by wayof a passage |0|, formed in the pipe bracket 95, and a brake cylinder pipe |02 with the brake cylinder device 34. The valve chamber contains a release valve element |04 that ris normally held in seated position under the force of a spring |05 disposed in the valve `chamber and is movable to unseated position upon energization of a. magnet |01 to establish communication from the chamber |00 tothe atmosphere by way of an exhaust port |08. The'application magnet valve portion 91 has formed'therein a valve chamber which communicates by way vof a supply pipe I 2 withy a suitable source of supply of fluid under pressure, such as a main reservoir I3, which may ofcourse be carried on the locomotive together with the brake valve device 52.

The supply pipe ||2 is adapted to extend throughoutthe train as does the control pipe 5| previously described. Mounted in the valve chamber is a supplyA valve member ||5, which is normally held in seated lposition as shown is transmitted therefrom through the me-` dium/of'the hanger member 25 to the pin 26` pressure of' iiuid in a chamber |22 communicat- Operation When the brake equipment shown in Fig. 1 is conditioned for operation, fluid under pressure vsupplied to the reservoir ||3 in the usual manner flows therefrom through the pipe ||2 to the valve chamber in the magnet valve `device 54, while with the brake valve device 52 in release position, the control pipe is connected to the atmosphere. If it is desired to effect an application of the brakes, the self-lapping brake valve device 52 is moved toward application position to effect supply of uid under pressure from the reservoir ||3 to the control pipe 5| according to the desired degree of application of the brakes. Fluid under ypressure flowing from control pipe 5| to diaphragm chamber 630i the control switch device 50 thenI acts against the diaphragm 68 to cause downward movement thereof, together with the followery member '|53 and stem 1|, against the force of the spring lll, so that the lever is tilted in a counterclockwise direction about the pin T1, while the clevis portion 82 of the lever forces theV rod 83 upwardly until the switch contact member 88 is carried into engagement with the contact element 92.

With the vcontact member 88 in engagement with the contact element 92, an electricy circuit is closed for effecting energization of the application magnet ||l| of the magnet valve device 54, which circuit includes the positive terminal of a battery or other source of power |30, a conductor ISI, the application magnet I||, a conductor |22, the switch contact elements 32 and 88. and a return conductor |33 leading to the negative ,terminal of the battery. Upon energization of the application magnet IIT, the valve |5 is moved away from its seat against the force of the spring IIB, and fluid under pressure previously supplied to the chamber is then conducted therefrom by way of the passage llll and pipe H32 to the brake cylinder device 36, the piston of which is thereby actuated to force the piston rod 33 outwardly. As the piston rod 33 is thus moved outwardly or to the left as viewed in Fig. l, it carries with it the pin 32 and brake lever 3|, which lever is thereby operated to force the brake shoe l1 into engagement with the wheel I0, whereupon the lever 3| is fulcrumed at the pin 30 and is further operated to pull the connecting rods 39 to the right as viewed in the drawings, while the brake lever 42 is operated to bring the brake shoe i5 into engagement with the opposite side of the wheel, the lever 42 being fulcrumed at the pin M.

Assuming that the wheel l5 of the vehicle is at this time rotating inV a counterclockwise direction, and that the brake shoes I6 and I1 are applied to the wheel li) in the manner just explained with normal force, it will be apparent .that the torque exerted on the brake shoe carriedby the lever 21, which lever is, however, prevented from tilting under the effect of such force by reason of engagement of the clevis pory tion v62 thereof with the stop lug 65 on the cas-; The torque` ing 56 of `the control switch device. exerted on the brake shoe I6, on the other hand, eifects downward displacement of that shoe, to-

gether with the hanger lever I9 and pin l2l), so' that .the lever 2| is tilted to a degree corresponding with the torque .thus produced about the piny 22, theend v63 of the lever being thus raised in opposition to the pressure of fluid in the chamber 59 exerted downwardly through themedium of the diaphragm 68, follower member 10, stem' portion spring 14.

thereof and the shock absorbing Meanwhile, the pressure of fluid supplied in the manner just explained to the brake cylinder pipe .|02 flows therefrom by way of pipe |23 to the chamber |22 in the fluid pressure switch device |20, with the result that the piston |2| is moved upwardly against the force of the light spring |24 vto raise the contact mem y ber |25 into bridging-engagement with the contact elements |21, Y'

It should be understood that the various elements of the brake control equipment constructed in accordance with my invention, including the magnet valve device M, control switch device 5|), and the levers 2| and 21 connected to the clasp brake rigging, are so proportioned and arranged .that the pressure of fluid supplied to the i brake cylinder device 34, by operation of the application magnet valve device Sl, effects theapplication of thevbrake shoes IS and I7 to the wheel to produce a torque on'the brake shoe rigring resulting in an Vupwardly directed force on the follower member 'I0 of the control switchy device 50 which force is suilicient` tofovercome the downwardly directed pressure of fluid inthe chamber 69 acting on the diaphragm 58 at sub-1 stantially the same time asthe effective braking -force' applied to the vehicle wheelreaches a de'-` sired value, corresponding to Athe increase in pressure of fluid in the control pipe 5| under the ccntrol'of the brake valve device 52. When the upward force on the follower member 10 resulting from the torque produced on the corresponding brake shoe as just explained thus becomes greater than the pressure of fluid in the chamber 69 effective on the diaphragm 68, the follower member, diaphragm'and stem 1| are con-- sequently carried upwardly and tilt the lever '|3- in a clockwisel direction about the pin 11,-the

lever at the same time pulling the rod 83 down- If the coefficient of friction between the brake;v

shoes and the wheel remains substantially constant for all speeds of rotation of thevehiclel wheel, there will be substantially no further', variation in torque force transmitted to the con-'i trol switch device 50, and consequently theapplication valve ||5 `of the magnet valve device '54 will remain seated, so that the pressure of fluid ber 410 upwardly a suilicientk distance to effect rotation of the lever` 16 about the pin 11 untilv the` rod 83 brings the switch contact member 88 into engagement with the contact element 89. Since theiluid pressure, operated switch contact member |26 is already inengagement with the contact elements |21, rthis operation of the control switch device 50 effects closing of the circuit for energizing the release magnet 01 of the magnet valve device 54, the circuit including the f positive terminal of the battery |30, conductor I 3|, the connected switch contact members |21V and |26, a conductor |40, the magnet |01, a conductor |4|,lthe contactmembers 88 and 89. and the return conductor `|33 connected to'the'negative terminal of the battery. l When the magnet |01 of the magnet valve device is thus energized, the release valve |04 is moved from its seat against the vpressure of the spring |05, and fluid under pressure is then vented from thelbrake cylinder device 34 through the pipe |02, passage I0|, chamber |00, past the unseated valve and through the discharge port |08. At this time,.however, the pressurevof fluid. in brake cylinder device 34 and in the chamber |22 of the fluid pressureactuated switch device is not reduced sufliciently to permit with:v

drawal of switch contact member |26 out oi engagement with the contact element |21, it belng understood that the spring |24 is designed to exert sufficient force to disengage the contact, members only when brake cylinder pressureis reduced 'substantially to atmospheric pressure.

Meanwhile, as `the braking force applied by the brake cylinder device 34 is gradually reduced, the torque transmitted through the medium ofthe shoe I6. hanger `member I9 and lever 2| tothe follower member 10 of the control switch device is correspondingly reduced, and with the control pipe pressure in chamberl 69 maintained un! changed, the diaphragm 68 is again operated to.v movethe ,follower memberr 10 and thereby ef. fect turning of the lever 16 and upward move` ment of the rod 83 untilthe switch contact member 88 is again moved to its intermediate position, thereby braking the circuit for the release magnet |01. The release Valve |04 is as a result movedl to seated position by springl |05 for cutting olf` further discharge of fluid under pressure from the brake cylinder 34. The brakes are thus .still held against the wheel with suflicient force, in relation `to the increased coemcient of I friction, to continue the desired retarding el-V fect on the vehicle as determined by the pressure of fluid in the control pipe 5| e e Ifvthe composition of material from which the regulates the braking force on the vehicle wheel wardly to eilect counterclockwise rotation of the lever 16and upward movement of the rod 83-for causing engagement of the switch contact membei` 88 and contact element 92, thereby reestablishing the circuit for energizing the application magnet ||1, whereupon fluid under pressure will be further supplied from the supply pipe ||2 to the brake cylinder device 34 for increasing the force of application of the brakes. When the force due to braking torque again balances the control pipe pressure exerted on the various elements of the control switch device 50 the magnet Valve device 54 will again be operated to cut off the supply of fluid' under pressure to the brake cylinder 34 as hereinbefore explained.

Thus, whether the coeilicient of friction between the brake shoes I6 and I1 and wheel I0 is substantially constant, increases, or decreases in response to the variations of rotative speed of the vehicle wheel, the torquemechanism is automatically effective to regulate the pressure in the brake cylinder device 34 to a value producing a braking effect corresponding to the pressure of iluid in the control pipe 5|. Accordingly, if the the torque control mechanism automatically regulates the braking force of the` vehicle wheel to` a correspondingly high value; if the pressure established in the controlpipe vis relatively low,

then the torque control mechanismv automatically to a correspondingly low value. It will be apparventthat the control exercised by the torque responsive mechanism automatically compensate for dilerences in the coeiiicient'of friction between the brake shoes and the wheel of different wheel `and axle assemblies, the associated brake .rigging mechanism regulating the fluid pressure in each brake cylinder to a value resulting in a substantially uniform torque on the cor- "justs and regulates the pressure yin the brake brake'shoes I6 and l1 are made is suchthat the l,

coemcient of friction reduces with the. reducing speed of rotation `of the vehicle wheel I0, instead of increasing as in the case of the operation previou'sly explained, the force exerted on the fol-v lower member 10 of the control switch device 50 resulting from brakingy torque will becomeless than the pressure of fluid in the chamber 69, so that the follower member will be moved down-` cylinder `14 to correspondingly different values, the operation in such casev being 'readily under-` standable from the description hereinbefore presented. The engineer may, of course, effect the release of the brakes at any time by. operating the self-lapping brake valve device 52 to reduce the pressure of fluid injthe control pipe 5| to that of the atmosphere. The operating elements of the control switch` device 50 are then actuated in the manner already explained to close the circuit for energizingthe release magnet |01 of themagnet valve device 54, the magnet |01 being this .time maintained energized for holding the disbrake control equipment is operative in the man.

ner described regardless of the direction of rotation of the wheel I0, it being understood that when the wheel I0 is rotated in a counterclockwise direction while the brakes are applied, braking torque is transmitted through the medium of the brake shoe I1, hanger lever 25, and lever 21 to the control switch device 50.

Although the mode of operation of the brake control means disclosed in Fig, 1 of the drawings already described is preferred', it should be understood that the equipment embodying the invention may, if desired, be designed to respond to another resultant force in addition to braking A torque set up during' application of the brake shoes to the wheel. The other resultant force referred to is the downwardly directed force produced by the clasp arranged brake shoes in seeking positions farther down on the treads of the wheel, when subjected to yheavy Vbraking force tending to draw the shoes toward each other below the horizontal center line of the wheel. Referring to Fig. l, and assuming that the brake shoes |6 and I1 are applied to the wheel I8 while the wheel is rotating in a counterclockwise direction, the force to which the brake shoes are subjected being sufficient to cause both-shoes to creep downwardly along the wheel tread, it will be apparent that both levers 2| and 21 will thereby be turned about their respective pivotal connections with the side frame so that the clevis portion 62 of lever 21 and the end 63 of lever 2| are carried upwardly against the spring 14 for moving the follower member 10 and diaphragm member 68 in opposition to the pressure of fluid supplied to the control pipe 5|. The force exerted on the mechanism of the control switch device through the medium of the lever 2| will` probably be greater than that effected by movement of the lever 21, due to the additional force resulting from torque acting through the medium of the brake shoe I6, but the resultant or composite force transmitted through the follower member will in any event be in a direction tov j oppose the control pipe pressure. The further operation of the brake control equipment, with the control switch device designed for operation in accordance to the opposing forces of fluid pressure in the control pipe 5| and 'theresultantv forces just referred to, will be understood from the description hereinbefore presented.

Equipment shown in. Figs. 4 to 7 In Fig. 4 of the drawings there is disclosed a'r vehicle brake equipment embodying the invention in a different form. The equipment includes a disk brake mechanism. |58 for applying braking force to a wheel |5I, a torque responsive device |52, a control switch device |53, the fluid;-

pressure switch |20, magnet valve device 54, and self-lapping brake device 52 shown in Fig. 1 of the drawings and hereinbefore described.

The brake mechanism |50 is similar to that shown and described in my application fora patent for a brake mechanism led in the U. S. Patent Oflice April lli, 1938, Serial No. 201,866, and is shown in Figs. 4 and 6 in association with a vehicle truck that is illustrated in fragmentary form as comprising a side frame structure |55 having the usual pedestal jaw members |56 between which is slidably guided a journal structure |51, and further including an. equalizer member |58 which is supported on the journal structure and carries the side frame structure through the medium of truck'springs such as that indicated at |59. Asis best shown in Fig. 6, the

,wheel |5| is secured to an axle |6| having an end portion i6 la thereof extending outwardly of the journal structure |51. Surrounding a poiably mounted'on the hub portion |65 is a housing |10, which has a flange portion l1! disposed on the lhub portion intermediate the collar |66 and the ring member |61. The housing |10 has formed thereon oppositely disposed Ventilating ducts |13, and also carries a projectingtorque arm portion |10 having a rounded end portion |15, which, as shown in Fig. 4 of the drawings, is adapted to be anchored within the torque responsive device |52 hereinafter described.

Disposed 'within the housing |10 and' keyed or otherwise secured to the end |16|a of the axle is rotor |16 carrying a plurality of annular braking plates or friction disks |11, which are respectively secured to the rotor by means of a plu- Arality of rods |18, each ofthe disks havin-g suitably apertured lugs for receiving the rod. The friction disks |11 are adapted for sliding movement along the rods |18, and are normally held in the positions shown in the drawings by a plurality ofsprings |19 interposed between the lugs formed on the disks and surrounding the respective rods |18. The friction disks |11are arranged in interleaved'relation with a plurality r` of stationary brake elements or friction disks IBI,

which are slidably mounted on a plurality of rods |82 carried by the housing |10 and are normally held out of engagement in the adjacent friction disks |11 by the force of a plurality of springs |83.

The several rotatable friction disks 11 and stationary friction elements |8| are adapted to be pressed together for creating braking force on the associated wheel and axley assembly by operation of a flexible diaphragm |85, which is mounted in a portion |86 of the housing structure |10 and is subject to the pressure of fluid supplied to a chamber |88 communicating with a supply pipe |88. The diaphragmr isen- -gaged at the side thereof opposite that exposed to the chamber |288 by a follower plate I8 which carries a plurality of adjustable screw-threaded elements |92 engaging the outermost stationary friction element |8 Referring again to Fig. 4 of the drawings, the

,torque responsive device |52 comprises a casing |14 projecting from the brake mechanism housing, which rounded portion of the torque arm is f interposed between and engages a pair of oppositely` disposed follower members 20| that are operatively mounted within the casing. Each of -the follower members 20| is normally adapted to engage one of a pair of annular collar portions 202 formed within the casing and is mounted in engagement with one of a pair of flexible diaphragms 206, each of which is clamped between thecasing |05 and a cover plate 206 that is secured by means of bolts 201 to the casing. The iiexible diaphragms 204 are each exposed to one of two pressure chambers 208 which are defined within the respective cover plates 206 and are connected together at all times by way of a passage 2 I0. The chambers 208 communicate with a 'i conduit 2I2 which, together with the chambers, is vadapted to be lled with a suitable pressure transmitting liquid, such as ,oil or glycerin, for

a purpose hereinafter explained.

The control switch device |53 is illustrated in Figs. 4 and 7, and comprises a casing 2|5 and having secured to an inner wall thereof aplate member 2|6, which is held in place by means of 'a plurality of bolts such as that indicated by the `character 2|1 in Fig, '1. The bolts 2|1 project `into the casing'2l5 and are adapted to carry an outer plate member 220 and an intermediate plate member 22|, the plate member `22| being separated from the plate member 2|^B by means of bushings 222 carriedk on the lrespective bolts 2|1, and the outer lplate member being interposed between the heads of the bolts and bushingmembers 223 which bear against the intermediate plate member 22|. A shaft 2'25 is rotatably mounted in suitable journal bores formed .in the plate members 2|6 and 22|, and has an extension 226 extending through an aperture 'in the plate member 220, over which extension is fitted a hollow shaft 221 which is journaled in the plate members 22| and 220.

Secured to the extension 226 ofthe shaft 225 is a switch arm 230, which is preferably formed of an insulating material and carriesa pair of switch contact elements 23| and' 232 adjacent the ends thereof, and which also has pivotally,

connected theretofby means of a pin 234 carried intermediate the contact elements,` a mov.

able contact member 233 that is adapted to be tilted about the pin into engagement with either of the contact elements 23| and 232. As isbest shown in Fig. 4,' the movable contact member 233 is normally urged toward a position in which it engages the contact element 23| by the force of a tension spring'235 which `is connected to the contact member 233 and to the switch arm 230. A suitably insulated switch arm 231 is secured through the other shaft '221 as is best shown in Fig; '1 of the drawings, and is provided with' an offset lug portion 238'eng`ageable with the outer end `of the movable contact member `233 and operative to force the contact member into engagement with the switch contact element- 232 when the two switch arms 231 and 230 are positioned as shown in Fig. 4, under 'operating conditions hereinafterexplained.

For actuating the switch arms" 230 and 231, the respective shafts 225 and 221 have formed thereon pinion portions 240 and 24|, as illustrated in Fig. '1. The pinion portion 240 is intermeshed with the teeth of a rack member`243 which is rotatably mounted on a shaft 244 carried by the plate members 2|6, ,22| and 220. The' rack member has an arm portion 245 pivot- Vally connected through the medium of a link 246 to the free end of a Bourdon tube 248, the other end of which is suitably anchored in the `casing 2l5 and is connected with the conduit 2|.2 containing the pressure transmitting liquid.

lThe Bourdon tube 248 is of the usual curved form, oval in cross-section, and is adapted to flex outwardly upon an increase in thevpressure `of fluid, therein. Similarly, the pinion portion 24| lof the shaft 221 is operatively meshed with the teeth of a rack member 25|, which is pivotally mounted on the shaft 244 and has an ex-y tension or arm 253 which is pivotally connected through the medium ofa link 252 to the outer ltrol pipe 5| and to the Bourdon tube 254 communicating therewith quickly expandsthe Bour- 'the contact element 232 lend'of a Bourdon tub'e 254, the other end of which is anchored in the casing 2|5 and communicates With the control pipe 5|.

, Operation The braker control equipment is illustrated in Fig. 4 as conditioned for operation, it being understood that the'torque arm |14 of the disk 'brake housing |10 is maintained in thel normal position as shown due to the opposing forces exerted on the rounded end portion |15 by the two diaphragms 204, which are held` in, their normal positions due to inherent tension. The chambers 208 thus contain maximum volumes of the liquid which also yi'llls the conduit2|2 and the `Bourdon tube 248 as hereinbefore explained.- The Bourdon tube 248 is at the same time disposed in its retracted position, wherein n the link 246, -rack member 243, 'and shaft 225 are held in the normalposition as shown in Fig. 4, theswitch'arm 230 carried by the shaft being adapted to rest on'a stop pin 260 secured to the casing. f .i A i With the equipment thus conditioned for operation, the control pipe; 5| is connected tothe katmosphere through suitable passages in the self-lapping brake valve device 52, so that the vBourdony tube254 connected to the control pipe don tube, the outer Vend` of which moves `the link 252 upwardly, as viewed in Fig. 4, so thatthe Y rack member 25| is turned in a counterclockwise direction about the pin 244 for rotatingthe shaft 225 andjextension226 in a clockwise direction. As-the shaft extension 226 is thus` turned in a clockwise direction, the switch arm 231 secured thereto is carried with it so that the lug 238 is withdrawn-from engagement With the movable contact member 233, which is thereupon tilted about its pivotal connection with the switch arm 230 under the force of the spring 235 until it engages the contact element 23|, as shown `in Fig. 5 of the drawings. With the movable contactmember 233 in engagement with the contact4 element 23|, the magnet ||1 of the application magnet valve device 91 becomes energized through' a circuit including a'grounded conductor 210 connected to the positive terminal of a battery 21|, a grounded conductor 212 connected to the magnet ||1, a conductor 213, the switch contact element and member 23| and 233, and a conductor 215 leading to the negative terminal of the battery.

Upon energization of the magnet ||1 as just explained, thesupply valve ||5 is moved to unseated position against the force of the spring l I6, vsowthat uid 4under pressure is then y'supplied from the main reservoiry pipe 2 past the unseatedvalve and through the passage |0|' and pipe |89to the diaphragm chamber |88 ofthe disk brake mechanism, shown in'Flg. 6. The pressure of iiuid thus supplied to the vchamber tact member |25 to bridge the contact elements When the rotating friction disks |11 and the non-rotatable friction disks |8| carried by the housing |15 are thus brought into fricticnal engagement, the housing |10 is subjected to a torque proportional to the braking force applied,

and a resultant force is consequently transmittedv through the medium of the torque arm portion |14 of the housing and the rounded end portion |15 to one of the follower members 20|, depending upon the direction of rotation of the wheel |5|, as will readily be understood. The flexible diaphragm 254 adjoining the follower member 23| thus subjected to the resultant force effected .A4,

by braking torque is thereby operated to displace a quantity of the liquid from the adjacent chamber 283, and the consequent increase in pressure of the liquidin the conduit 212 and in the Bourdon tube 248 communicating therewith causes expansion of that member for pulling the link member 245 upwardly, as viewed in Fig. v4. The link member 256 in so moving actuates the rack member 243, shown in Fig. 7, and thereby acts through pinion 245 to turn the shaft 226 for rotating the switch member 23B in a clockwise direction and toward the other switch member 231, which has already been moved from its normal position as shown in Fig. 5.

As the switch arm 233 thus approaches the switch arm 231, the movable switch member 233 is brought into engagement with the lug 238 of the switch arm 231 and is then turned about its pivotal connection with the switch arm 233 against the force of the spring 235 until the, connection between the contact member and the contact element 23| is broken. The circuit for the application magnet ||1 of the magnet valve device 54 is consequently opened, andthe spring H5 is then enabled to move the supply va-lve i5 into seated position for cutting off supply of fluid under pressure to the disk brake mechanism |50.

It will thus be apparent that the control switch device |53 is cooperative with the magnet valve device 54 tomaintain the brake mechanismv l5() if,

in an application position under a braking force determined in accordance with the pressure of fluid in the control pipe 5|, the chosen degree of application of the brakes remaining unchanged so long yas the coemcient of friction between the rotatable brake disks and the stationary brake disks remains substantially constant. If, on the other hand, the coemcient of friction between the interleaved brake or friction disks increases or decreases during the application, the torque arm |14 will be correspondingly shifted farther away from its normal position or back toward its normal position for effecting corresponding partial release of the brakes or increased force of application thereof, las the case may be.

In the event of increase inthe coefficient of friction between the interleaved friction disks of the disk brake mechanism- |55, for example, the torque arm |14 is further displaced from its normal position for effecting an increase in the control pipe pressure.

pressure of liquid in the corresponding chamber 238 and in the conduit 2 2 and Bourdon tube 248, whichv tube is thereby again expanded to effect further clockwise rotation of the switch arm 230 until the contact member 233 is again tilted into engagement with the contact element 232. The release magnet |01 is then energized through a circuit including the positive terminal of battery 21 I, grounded conductor 21D, a grounded conductor 219, contact elements |26 and |21, the magnet, a conductor'28|, contact elements 232 and. 233, and conductor 215. The valve |04 is accordingly unseated to eiect discharge of uid under pressure from the disk brake mechanism |59 for effecting partial release of the brakes.

On the other hand, if the coefficient offriation between the friction disks of the brake mechanism |53 decreases as the speed of the vehicle wheel decreases, the torque arm |14 is proportionately vrelieved of braking torque, so that the diaphragm 234 previously displaced thereby is `permitted to move toward its normal position for reducing the pressure of liquid in the chambers 258, conduit 2 I2 and Bourdon tube 248. With the pressure of liquid in the Bourdon tube 248 thus reduced, the tube is permitted to retract toward its normal position, and through the medium of the associated rack member and pinion to effect movement of the switch Iarm 230 away from the still stationary switch arm 231 until the movable switch contact member 233 is returned by the force of the spring 235 into engagement with the contact element 23| When the switch contact member 233 engages the element 23|, the application magnet H1 again becomes energized by battery 21| through the circuit already described. The supply valve thereby unseated for supplying sufficient fluid under pressure by way of Vpipe |39 to the brake mechanism |53 to maintain a substantially constant braking effort corresponding to the pressure established inthe control pipe 5|. l

It will be understood that if the operator desires to Vincrease the degree of application of the brakes, he may eect a further increase inthe pressure of fluid in the control pipe 5|, whereupon thecontrol switch device |53 will again become operative in the manner hereinbeforeex-` plained to cause further supply of fluid under pressure to the brake mechanism |50, while the torque responsive mechanism |52 will again function to insure that the braking force applied to the wheel of the vehicle corresponds to the Y In like manner, the operator may effect a partial release of the brakes by causing a reduction in the pressure of fluid in the control pipe 5|. l

When it is desired` to effect the complete release of the brakes, the self-lapping brake valve device 52 is operated to effect reduction in the pressure of fluid in the control pipe 5!l to that of the atmosphere, so that the Bourdon tube 254 communicating therewith is allowed to retract for causing rotation of the switch arm 231 in a counterclockwise direction, the outer lug 238 of.

the switcharm being thus carried into engage ment with the movable switch vContact member l233 for positioning it in engagement withthe conway of the unseated release valve |04 in the manner already explained.v As the force with which.

the brakes are applied is thus reduced, the torque responsive mechanism |52 functions 'to'effect reduction in the pressure of liquid .inl' the conduit 2| 2 Aand inthe Bourdon tube .248, so that that tube is permitted to retract along'with'the Bourdon tube 254, while the switch arm 236 is moved in a counterclockwise direction ytoward its normal position. When the pressure'of` fluid in the operating4 diaphragm lchamber |88 of the brake mechanism |56, shown in Fig. 6, has been reduced understood that a brake control` equipment including features of the invention may be adapted for use withany Vdesired type of truck brake `mechanism for `effecting various degrees of lappllcation ofV the brakes under the controly of iiuid -pressure in a control pipe, the brakingv torque produced during a brake application being uti- 4lized to insure a substantially constant retarding force, on the vehicle wheel'corresponding to the control pipe pressure. It will furtherbe apparent that the various elements of the control equipjment, such as the control switch device andthe electrically operated supply and release valve device, may be conveniently located in different positions on a vehicle truck, or if preferred may .be embodied in a unitary device adapted to be carried'by a suitable mounting bracket.

Although I have described two embodiments of :the invention indetail, it is not my intention to limit the scope thereof to those embodiments or otherwise than by the terms of the appended claims.

Having now described myginvention, what I claim as new'and `desire to secure by Letters ,Patent is: t l

1. In a brake mechanism for a railway truck `having a wheel, in combination, a rbrake element operatively mounted for braking engagement with a braking surface rotatable with the wheel, .fluid pressure actuating means for operating said brake element, means for supporting said controlling the supply and release of fluid under pressure to and from said iiuid pressure actuating means including an element operatively interposed between said movable abutment and said torque responsive lever, said means being constructed and arranged to produce a retarding force which is maintained in proportion to said controlflud pressure. n

2. In a brake mechanism for a railway truck having a Wheel, in combination, a brake element 4 operatively mounted for braking engagement with `a braking surface rotatable with thewheel, fluid pressure actuating means for operating said `brake element, means for supporting said brake element from the truck includingy a pivotally mounted lever subject to a resultant force due to braking torque produced upon engagement of the brake element with the brakingsurface, a movable abutment subject to acontrol fluid pressure ipressureto and from said fluid pressure actuating means as to establish and maintain a retarding force according to saidcontrol uid pressure.

3. In a brake mechanism for a railway truck having a wheel, in combination, a brake element operatively mounted for braking engagement with a braking surface rotatable with the wheel, fluid pressure actuating means for operating said brake element, means for supporting said brake element from the truck including a pivotally mounted lever subject to a resultant force due to braking torque produced upon engagement of the brake element with the braking surface, a movable 'abutment subject to a fluid pressure variable in accordance with any desired degree of application of the brakes, electroresponsive valve means controlling the supply and release of fluid under pressure to and from said fluid pressure means, and control switch means controlling circuits for said electroresponsive valve means and operative in accordance with relative movement of vsaid movable abutment and of said torque responsive lever.

y 4.7In a brake mechanism for a railway truck having a wheel, in combination, a brake element operatively mounted for braking engagement with a braking surface rotatable with the Wheel, fluid pressure actuating means for operating said brake element, means for supporting said brake element from the truck including a pivotally mounted lever subject to a resultant force due to braking torque produced upon engagement of the brake element with the braking surface, a movable abutment subject to a fluid pressure vvariable in accordance with any desireddegree of application ofthe brakes, switch means subject to opposing forces exerted through the medium of said movable abutment and said torque responsive lever, said switch means being operative by said movable abutment for closing an application circuit and operative at another time'by said lever for closing a release circuit, and electroresponsive valve means operative upon energizationof said application circuit to supply fluid under pressure to said fluid pressure brake actuating means and upon energization of said release circuit to 4vent duid under pressure therefrom.

5.4In a brake mechanismfor a railway truck Ahaving ta lwheel and braking means including a pair of brake elements arranged in clasp relation with the wheel below the horizontal center line thereof, in combination, lever means supporting -said brake elements from the truck and subject to forces resulting from downward displacement of said brake elements lalong the tread of the wheel when said elements are subjected to relatively heavy vbrake applying force, a movable abutment subject'to a u'id pressure variable in accordance in any desired degree of application of the brakes, and means subject to the oppos-` ing forces exerted'by said movable abutment and by said lever means'for controlling the force with which said brake velements are applied to the wheel.

6. r Control apparatus for a vehicle brake equipment comprisingv a. torque member subject to braking torque produced during an application of the brakes, movable abutment means operative by said torque member for establishing a fluid pressure corresponding to said braking torque, means operable to establish a control fluid pressure variable in accordance with any desired degree of application of the brakes, a Bourdon tube subject to the iluid pressure corresponding to braking torque, another Bourdon tube subject to said control fluid pressure, and electromagnetic means conditioned according to relative movement of said Bourdon tubes for controlling the application vand release of the brakes.

7. In a brake mechanism for a railway truck having a wheel, a plurality of brake elements arranged in clasp relation with said wheel, and fluid pressure means for operating said braking elements; in combination, lever means pivotally `mounted on the truck for carrying said brake elements and adapted to be subjected to braking torque upon application of said elements into braking relation with the wheel, movable abutment means subject to a control fluid pressure variable in accordance with any desired degree of application of the brakes, a movable member operatively interposed between said abutment means and said lever means, and valve means controlled in accordance with movement of said movable member to establish and maintain a retarding force determined by said control pressure, saidvalve means being operative in response to an increase in said control pressure for supplying iluid under pressure to said uid pressure means, and operative in response to an increase in braking torque to a degree exceed'- ing the force of said control pressure for venting fluid from said fluid pressure means.

BURTON S. AIKMAN.

CERTIFICATE 0F CORRECTION.- Patent No. 2,27%).152. April lll., 1911.2.

` BURTON s, AIRMAN.

It is hereb;r certified that error appea'rs'in the printed specification ofthe above numbered patent requiring correction as follows: Page l9, `irst column, line 8, claim 6, for "electromagnetic" read electrpneumatc; and that the said Letters Patent shouldbe readwth this correct o'n therein-that the same may conform to the record of the oase in the Patent Office.

Signed Rnd sealed this 5rdl day of November, A. D. 19).;2.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

